1. Field of the Invention
The present invention relates to an improvement of a lubricating structure in an internal combustion, and particularly of an internal combustion, comprising a rocker shaft holder which comprises a plurality of shaft-supporting sections disposed at distances in a direction of arrangement of cylinders and connected together and which is fixed to a cylinder head, and rocker shafts each of which has a plurality of rocker arms swingably carried thereon and which are supported by the shaft-supporting sections, as well as of an internal combustion comprising rocker shafts each of which has a plurality of rocker arms swingably carried therein and which are supported on a rocker shaft holder fixed to a cylinder head, valve-operating characteristic changing mechanisms provided in the rocker arms and capable of changing the operating characteristic for engine valves by changing the hydraulic pressure, and a hydraulic pressure control valve unit mounted to the cylinder head for controlling the pressure of a working oil supplied to working oil passages defined in the rocker shafts to lead to the valve-operating characteristic changing mechanisms.
2. Description of the Related Art
Such a rocker arm lubricating structure in an internal combustion engine is conventionally known, for example, from Japanese Utility Model Publication No. 7-7524.
In the prior art disclosed in the above Japanese Utility Model, a pipe member extending in a direction of arrangement of cylinders is fixedly dispose above a valve-operating mechanism to guide a lubricating oil to slide portions of rocker arms, so that the lubricating oil is dropped from the pipe member to the valve-operating mechanism located below the pipe member. Therefore, the lubricating pipe member is required, resulting in an increase in number of parts.
Accordingly, it is an object of the present invention to provide a lubricating structure in a multi-cylinder internal combustion engine, wherein an increase in number of parts is avoided in the lubrication of slide portions of at least some of the rocker arms.
To achieve the above object, according to a first aspect and feature of the present invention, there is provided a lubricating structure in an internal combustion engine, comprising a rocker shaft holder which comprises a plurality of shaft-supporting sections connected together and disposed at distances in a direction of arrangement of cylinders and which is fixed to a cylinder head; and rocker shafts each of which swingably carries thereon a plurality of rocker arms and which are supported by said shaft-supporting sections, wherein said rocker shaft holder has an oil sump defined on its upper surface, and has lubricating oil passages communicating with said oil sump so that a lubricating oil can be supplied to slide portions of at least some of said rocker arms.
With such arrangement of the first feature, the oil accumulated in the oil sump in the upper surface of the rocker shaft holder integrally provided with the plurality shaft-supporting sections for supporting the rocker shaft and fixed to the cylinder head can be reliably supplied from the oil sump through the lubricating oil passages to the slide portions of at least some of the rocker arms to positively lubricate the slide portions of at least some of the rocker arms. Therefore, a part exclusively for lubricating the slide portions of at least some of the rocker arms is not required and hence, the slide portions of the rocker arms can be lubricated, while avoiding an increase in number of parts. Moreover, the oil sump is defined in the upper surface of the rocker shaft holder and hence, can be formed easily.
According to a second aspect and feature of the present invention, in addition to the first feature, said oil sump having a groove portion extending in the direction of arrangement of the cylinders is defined in the upper surface of said rocker shaft holder fixed to the cylinder head inclined to left or right in said direction of arrangement of the cylinders; said rocker shaft holder has a rib projectingly provided on its upper surface at a position below said groove portion to extend in the direction of arrangement of the cylinders; and said lubricating oil passages with their upper ends communicating with a portion of said oil sump closer to said rib are provided in said rocker shaft holder to extend through said rocker shaft holder along a side face of said rib adjacent said oil sump. With such arrangement, it is possible to compensate for a reduction in rigidity of the rocker shaft holder due to the provision of the lubricating oil passages, while enabling the supplying of the oil in the oil sump to the cylinders. Moreover, the rib can function as a wall defining a lower portion of the oil sump, whereby a larger amount of the oil can be positively stored on the upper surface of the rocker shaft holder.
According to a third aspect and feature of the present invention, in addition to the second feature, the lubricating structure further includes valve-operating characteristic changing mechanisms provided in said rocker arms and capable of changing the valve-operating characteristic for engine valves by changing the hydraulic pressure, and a hydraulic control valve unit mounted to the cylinder head to be able to control the pressure of the working oil supplied to said valve-operating characteristic changing mechanisms so that a drain oil discharged from said hydraulic control valve unit is guided to said oil sump. With such arrangement, the drain oil discharged from the hydraulic control valve unit is also passed to the slide portions of the rocker arms and utilized to lubricate the slide portions.
According to a fourth aspect and feature of the present invention, in addition to the first feature, at least a portion of said oil sump defined in the upper surface of said rocker shaft holder fixed to the cylinder head inclined to left or right in said direction of arrangement of the cylinders is defined by a plurality of bottomed cylindrical tubes integrally provided on said rocker shaft holder with lost motion springs accommodated therein for biasing some of the rocker arms; and a rib integrally provided on said rocker shaft holder to connect said bottomed cylindrical tubes together at a lower side in a direction of inclination of the cylinder head, and said lubricating oil passages are provided in said rocker shaft holder with their upper ends communicating with said oil sump in a region surrounded by the plurality of bottomed cylindrical tubes and said rib.
With such arrangement of the fourth feature, the connection of the plurality of bottomed cylindrical tubes to one another by the rib can contribute to an increase in rigidity of the rocker shaft holder, and define at least a portion of the oil sump on the upper surface of the rocker shaft holder. Moreover, the upper ends of the lubricating oil passages are put into communication with portions having the increased rigidity and hence, it is possible to avoid a reduction in rigidity of the rocker shaft holder due to the provision of the lubricating oil passages.
According to a fifth aspect and feature of the present invention, in addition to the fourth feature, the lubricating structure further includes valve-operating characteristic changing mechanisms provided in said rocker arms and capable of changing the valve-operating characteristic for engine valves by changing the hydraulic pressure, and a hydraulic control valve unit mounted to the cylinder head to be able to control the pressure of the working oil supplied to said valve-operating characteristic changing mechanisms so that a drain oil discharged from said hydraulic control valve unit is guided to said oil sump. In addition, according to a sixth aspect and feature of the present invention, in addition to the first feature, the lubricating structure further includes valve-operating characteristic changing mechanisms provided in said rocker arms and capable of changing the valve-operating characteristic for engine valves by changing the hydraulic pressure, and a hydraulic control valve unit mounted to the cylinder head to be able to control the pressure of the working oil supplied to said valve-operating characteristic changing mechanisms so that a drain oil discharged from said hydraulic control valve unit is guided to said oil sump.
With such arrangements of the fifth and sixth features, the drain oil discharged from the hydraulic pressure control valve unit can be also guided to the slide portions of the rocker arms and utilized for the lubrication of them.
According to a seventh aspect and feature of the present invention, in addition to the first feature, the lubricating structure further includes valve-operating characteristic changing mechanisms provided in said rocker arms and capable of changing the valve-operating characteristic for engine valves by changing the hydraulic pressure, and a hydraulic control valve unit mounted to the cylinder head for controlling the pressure of the working oil supplied to working oil passages defined in said rocker shafts to lead to said valve-operating characteristic changing mechanisms, and said oil sump enabling the drain oil to flow from said hydraulic pressure control valve unit is defined in the upper surface of the rocker shaft holder so that the lubricating oil can be supplied to the slide portions of at least some of said rocker arms.
With such arrangement of the seventh feature, the drain oil discharged from the hydraulic pressure control valve unit is supplied to the slide portions of at least some of the rocker arms via the oil sump in the rocker shaft holder supporting the rocker shafts. Therefore, a part exclusively for lubricating the slide portions of at least some of the rocker arms is not required and hence, the slide portions of the rocker arms can be lubricated, while avoiding an increase in number of parts. Moreover, the oil sump is defined in the upper surface of the rocker shaft holder and hence, can be formed easily.
According to an eighth aspect and feature of the present invention, in addition to the seventh feature, the lubricating structure further includes a passage-defining member interposed between said hydraulic pressure control valve unit and said rocker shaft holder, and having communication passages interconnecting said hydraulic pressure control valve unit and said working oil passages, an upper portion of said passage-defining member being formed to be able to deliver the drain oil discharged from said hydraulic pressure control valve unit to said oil sump. With such arrangement, the drain oil discharged from the hydraulic pressure control valve unit is supplied from the passage-defining member to the oil sump in the rocker shaft holder and hence, a part exclusively for delivering the drain oil between the hydraulic pressure control valve unit and the oil sump is not required.
According to a ninth aspect and feature of the present invention, in addition to the eighth feature, the upper portion of said passage-defining member is provided with a recess adapted to receive the drain oil from said hydraulic pressure control valve unit, and a guide for guiding the drain oil accumulated in said recess toward said oil sump, said guide being extending from said passage-defining member to above said oil sump. With such arrangement, the drain oil can be reliably delivered from the passage-defining member to the oil sump in the rocker shaft holder. Thus, a sufficient amount of the drain oil can be supplied to the oil sump to perform the sufficient lubrication.
To achieve the above object, according to a tenth aspect and feature of the present invention, there is provided a lubricating structure in an internal combustion engine comprising rocker shafts each of which has a plurality of rocker arms swingably carried therein and which are supported on a rocker shaft holder fixed to a cylinder head, valve-operating characteristic changing mechanisms provided in the rocker arms and capable of changing the operating characteristic for engine valves by changing the hydraulic pressure, and a hydraulic pressure control valve unit mounted to the cylinder head for controlling the pressure of a working oil supplied to working oil passages defined in the rocker shafts to lead to the valve-operating characteristic changing mechanisms, wherein the rocker shaft holder has an oil sump defined in its upper surface to enable a drain oil from the hydraulic pressure control valve unit to flow, so that a lubricating oil can be supplied to slide portions of at least some of the rocker arms.
With such arrangement of the tenth feature, the drain oil discharged from the hydraulic pressure control valve unit is supplied to the slide portions of at least some of the rocker arms via the oil sump in the rocker shaft holder supporting the rocker shafts. Therefore, a part exclusively for lubricating the slide portions of at least some of the rocker arms is not required and thus, the slide portions of the rocker arms can be lubricated, while avoiding an increase in number of parts. Moreover, the oil sump is defined in the upper surface of the rocker shaft holder and hence, can be formed easily.
According to an eleventh aspect and feature of the present invention, in addition to the tenth feature, the lubricating structure further includes a passage-defining member interposed between said hydraulic pressure control valve unit and said rocker shaft holder, and having communication passages interconnecting said hydraulic pressure control valve unit and said working oil passages, an upper portion of said passage-defining member being formed to be able to deliver the drain oil discharged from said hydraulic pressure control valve unit to said oil sump. With such arrangement, the drain oil discharged from the hydraulic pressure control valve unit is supplied from the passage-defining member to the oil sump in the rocker shaft holder and hence, a part exclusively for delivering the drain oil between the hydraulic pressure control valve unit and the oil sump is not required.
According to a twelfth aspect and feature of the present invention, in addition to the eleventh feature, the upper portion of the passage-defining member is provided with a recess adapted to receive the drain oil from said hydraulic pressure control valve unit, and a guide for guiding the drain oil accumulated in said recess toward said oil sump, said guide being extending from said passage-defining member to above said oil sump. With such arrangement, the drain oil can be reliably delivered from the passage-defining member to the oil sump in the rocker shaft holder. Thus, a sufficient amount of the drain oil can be supplied to the oil sump to perform the sufficient lubrication.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.